Generally, machines working in line, such as the ones just mentioned, have different operation rates, and particularly, the downstream machines operate faster than the machines situated upstream, to prevent hindrance to operation of the upstream machines and to provide a wider rage of variation in the processing rate of the product flow, for the reasons which will be explained in the following.
The machines are connected to one another by product conveyors, which in the case of the syringes, and similar articles, consist of downwards sloping tracks, along which the products slide to the next machine. The products are raised to the inlet of the sloping conveyors by suitable lifters, or by placing the machines at different levels.
In this operational context, product flow can be affected by short interventions made by the operator, for instance to replace an empty reel or band with a new one on the packaging machine, or to remove slightly jammed articles, or by longer stopping of the packaging machine, such as when the jammed products require a longer time to be removed or a most critical operation problem has occurred.
In the first case, shorter stop time, the articles accumulate along the sloping tracks of the conveyors, then when the packaging machine resumes operation, they are processed at a higher rate, so as to take a short time for the product flow to return to its regular condition.
To cope with the second case, longer stop time, temporary storing devices are placed along the conveyor, with the aim of storing a larger number of articles, to keep the upstream production rate unchanged for a longer time. Also in this case, the packaging machine operation is resumed, after the problem has been removed, at a higher rate, to empty the temporary storage device.
In case the temporary storage device gets full before the packaging machine operation is resumed, the facility must be generally stopped.
Also the known temporary storage devices, in case of syringes or similar articles, include sloping track sections carried by a rotary cylinder, also sloping. Once one track section is full with articles, the cylinder is rotated one step and a new track section is aligned with the sloping conveyor to be filled, and so on. Conversely, when operation is resumed, the cylinder is rotated one step when the currently available track section is empty, until all sections are emptied.
Accordingly, along the terminal section of the tracks the articles accumulate in a close reciprocal contact, and are then transferred to the inlet of the second machine either singly or in groups.
If this is acceptable for short rows of articles in normal operation condition, when a stop occurs for the packaging machine the row of articles becomes too long. Due to the sloping, the foremost articles are subjected to particularly urging force, so that they can become damaged, thus requiring removal of defective packages or causing new jamming later on, when operation is resumed. It should be considered that the sloping tracks may extend some meters, just for making available a suitable length of track for storing the articles during these short stops.
The same happens in the temporary storage device, which also may extend some meters in the longitudinal direction to allow sufficient room for the articles.